A firearm trigger serves the purpose of initiating the firing sequence of the firearm. Typically, upon actuating the trigger, a sear operatively connected thereto is disengaged from locking engagement with a hammer/striker or the firing pin of the firearm, which in turn strikes a round of ammunition within the firing chamber. The sensitivity of the trigger thus is of particular importance in the operation of the firearm. For example, too heavy a trigger pull generally is undesirable since it can lead to jerking of the trigger that can cause shifting or misalignment of the weapon immediately prior to firing and spoil the shooter's aim. On the other hand, too light a trigger pull can raise issues of inadvertent or unintentional discharge of the firearm, especially if dropped or otherwise jarred. Further, with multi-barrel firearms, the trigger pull must not be too light to avoid doubling, that is, an undesirable or unintentional release of a second striker, which can cause the firing of more than one round at the same time.
The trigger and sear generally are calibrated so as to provide an engagement between these parts that should insure a desired trigger pull or response. However, because of normal manufacturing tolerances, this engagement can vary from sharp to loose. This variation or looseness is described as trigger “take-up”. In addition, after extended use, further looseness or take-up can develop in the engagement between the trigger bar and the sear. Such “take-up” or looseness in the action of the trigger is undesirable from a user's standpoint since the accuracy of the shot depends in large measure on the responsiveness of the trigger, and thus the sharper the trigger response, the more accurate the marksmanship.
Some shooters accordingly will try to sharpen or adjust the responsiveness of the trigger to their own preferences, though often to such an extent that the firearm becomes unsafe without their realizing that the newly adjusted trigger setting poses a danger. Since the area of engagement between the trigger and the sear is such a small amount, typically between about 0.024 inches to 0.027 inches, measuring a setting typically requires the use of an optical comparator, and therefore, it is difficult for the user to determine the resulting new settings upon adjustment and the dangers that may result from a setting that is too small. Thus, resetting the firearm to the original factory setting or determining if the setting is safe generally is not possible for the ordinary user.
Thus, what is needed is an apparatus that enable easy and concise adjustment of various operating parameters of a firearm trigger assembly to a desired user setting to “sharpen” the trigger up to a minimum safe level of operation.